The escalation of both the frequency and magnitude of water stress and salinity is foreseen to manifest in numerous global regions within the framework of ongoing climate change (Chaudhry and Sidhu, 2022; Soares et al., 2022). Rising temperatures and changing precipitation patterns are projected to exacerbate existing water scarcity issues, while sea level rise and changing groundwater dynamics are expected to increase the incidence of salinity intrusion in coastal areas (Asif et al., 2023). As water stress and salinity stress become more common the impacts on agriculture, ecosystems, and human well-being are likely to become more severe (Semeraro et al., 2023). In response to these challenges, there is a growing need to develop adaptive strategies to mitigate the impacts of water and salinity stresses. These strategies may include improving water use efficiency, developing crop varieties that are more resistant to drought and salinity, encouraging sustainable land management strategies, and allocating resources towards the development of water treatment and desalination technologies are essential steps in fostering sustainable water resource utilization (Acosta-Motos et al., 2020; Albatayneh, 2023; Patel et al., 2023).

Water stress occurs when plants experience a lack of water, either due to insufficient rainfall, high temperatures, or other factors that increase evaporation. This can lead to reduced plant growth, leaf wilting, and even death in severe cases. Plants respond to water stress by reducing their stomatal openings to conserve water, which can also affect the photosynthetic process and reduce their ability to grow (Arve et al., 2011; Bodner et al., 2015). Salinity stress occurs when plants are exposed to high levels of salt in the soil or water. High salinity can lead to reduced water uptake by plants, which in turn can lead to reduced plant growth, wilting, and even death. Plants respond to salinity stress by developing mechanisms to exclude or tolerate salt, such as increased root growth or salt secretion (Acosta-Motos et al., 2017; Acosta-Motos et al., 2020). Both water stress and salinity can have significant impacts on agricultural productivity and ecosystem health. In some cases, plant breeders have developed crop varieties that are more resistant to these stresses, but in other cases, it may be necessary to implement management practices such as irrigation scheduling, soil amendments, or alternative crops to mitigate their effects (Paranychianakis and Chartzoulakis, 2005; Phogat et al., 2020).

Pistacia lentiscus, also known as mastic tree or lentisk, has potential uses in a context of climate change. As a drought-tolerant species, it is likely to be more resilient to water stress than many other ornamental plants, making it a good choice for landscaping in regions prone to drought (Bussotti et al., 2014; Leotta et al., 2023). Also, its deep roots and ability to thrive in poor soils make it a potentially useful species for erosion control and land restoration projects (Ramón Vallejo et al., 2012). In addition to its potential uses in a context of water stress and drought, Pistacia lentiscus may also have applications in regions affected by salinity stress. The species is known for its ability to tolerate high levels of salt in the soil and can even grow in saline soils near the coast. In areas affected by salinity stress, the use of Pistacia lentiscus as an ornamental plant in landscaping projects may be particularly valuable (Álvarez et al., 2018; Castillo-Campohermoso et al., 2020). The plant's tolerance to salt and its ability to thrive in poor soils make it a good choice for revegetation and erosion control projects in coastal areas (Parraga-Aguado et al., 2013). By incorporating Pistacia lentiscus into agroforestry systems, farmers may be able to improve soil structure, reduce soil salinity, and improve water use efficiency, leading to higher crop yields and greater resilience in the face of climate change. Finally, the species has been successfully integrated into agroforestry systems in Mediterranean regions, where it has been used for shade, windbreaks, and as a source of animal fodder (Williams, 2002). It is well-known that analysing individual stresses, such as water supply restrictions and salt stress, rather than their combination, can provide several advantages when studying their effects on plants. Studying individual stresses allows to isolate and understand the specific effects of each stress factor. This can help in determining the unique physiological and morphological responses of Pistacia lentiscus plants to each stressor drought stress and salinity. The purpose of this work was to study growth pattern, biomass and mineral distribution and the seasonal pattern of water status, photosynthetic rate and stomatal conductance in plant of Pistacia lentiscus grown under deficit irrigation and salinityto determine the ability and response of plant to cope with water and saline stresses, which represents a major factor in plant growth and survival in a context of climate change.

Climate change is affecting Mediterranean regions with extreme weather events, such as prolonged droughts and increases in soil salinity. These conditions can affect the capacity for grow and survive in plants, even for species that are adapted to these regions. Species that grow in Mediterranean regions, such as Pistacia lentiscus provide important ecosystem services such as ornamental production, soil protection, and carbon capture (Romano et al., 2022). Therefore, it is essential to find ways to protect and improve their capacity to adjust to changing conditions. The growth response of species to stresses is a complex expression of physiological and biochemical parameters. Although the tolerance mechanisms for salt and drought stress are similar physiologically and sometimes, they overlap, some aspects of a plant's physiology and metabolism may change if the plant is under salinity or water stress (Álvarez et al., 2018). In our conditions, we found that Pistacia lentiscus plants were more affected by deficit irrigation than by saline water. Concretely, different stresses induced different growth responses in Pistacia lentiscus, in this sense, both deficit irrigation treatments showed significant differences compared to the control and salinity in leaf/total DW and stem/total DW. However, the severe irrigation deficit treatments had differences in variables such as total DW, SLA (as measure of the proportion of plant biomass invested in leaf area but also of relative thickness, density or spread of leaves), LAR (as measure of photosynthetic surface relative to respiratory mass), or plant height (Wellstein et al., 2017; Gonzalez-Paleo and Ravetta, 2018).

Several variables and integrated them into a star and ray graph, which corroborated the differences between treatments indicated above were analysed. Aesthetically and commercially, customers appreciate a compact and architecturally balanced plant with increased foliage size in relation to plant height and with no alterations in leaf colour (Álvarez et al., 2013). Indeed, leaf colour is also an important attribute of ornamental plants, when used in gardening or landscaping projects, which influences its commercial value (Navarro et al., 2009). Customers associate yellow leaves with senescence, which is a negative trait that decrease the quality and attractiveness of the plant (Boutigny et al., 2020). In our conditions, no significant modifications in the leaf colour parameters were found and only treatment with moderate lack of irrigation had the highest value for the compactness variable. Therefore, the kind of stress should be taken into consideration as a key factor when using saline water and/or deficit irrigation as an irrigation strategy. This may affect the ornamental quality of the plants, assessed through growth parameters, to a greater or lesser extent (Koniarski and Matysiak, 2013; Sánchez-Blanco et al., 2019). Our results indicate that although both deficit irrigation and salinity reduced relative growth rate in Pistacia lentiscus, the time that each stress took to have an impact on plant growth differed significantly between salinity and water stress. Salinity affected growth much later than water stress, and such a reduction was only visible after a considerable amount of time had passed since the beginning of the irrigation treatments, as salts take time to accumulate inside plants before the concentrations reach dangerous levels and influence plant function (Munns and Tester, 2008). This underlines the fact that the duration of the water and salt stress is a crucial factor (Álvarez and Sánchez-Blanco, 2015; Vivaldi et al., 2021).

Sodium (Na⁺) and chloride (Cl^-) are two ions that can accumulate in plant roots, particularly when plants are exposed to high levels of salts. When salt is present in the soil, the plant roots take up both water and salt. Sodium and chloride ions are particularly mobile and can easily move into the root cells. High concentrations of Na⁺ and Cl^- in the root cells can create an osmotic imbalance, leading to reduced water uptake and increased water stress. Additionally, high levels of Na⁺ in the plant can compete with other essential cations, such as potassium (K⁺) or calcium (Ca²⁺), for uptake and transport, leading to nutrient imbalances and potential toxicity (Acosta-Motos et al., 2016). A low K⁺/Na⁺ and Ca²⁺/Na⁺ ratios can cause several physiological changes in plants, such as reduced photosynthesis, nutrient imbalance, and oxidative stress, which can negatively affect plant growth and productivity. Sodium and potassium interact on two levels: interference with K⁺ nutrition and replacement of Na⁺ for K⁺ (Haro et al., 2010). High Na⁺ concentrations in plants cause K⁺ shortage symptoms and impair several K⁺-mediated physiological activities, including protein synthesis and enzymatic responses. Furthermore, membrane depolarization generated by Na⁺ input into the cell impairs K⁺ uptake through inward-rectifying K⁺ channels, making it thermodynamically unfavourable, as well as increased K⁺ outflow through outward-rectifying channels (Shabala et al., 2006; Coskun et al., 2013). Despite the controversy over whether NRT proteins transport NO^3–, K⁺ or both, it is evident that Na⁺ competes with K⁺ in plant uptake specifically through High-Affinity K⁺/K⁺ uptake/K⁺ Transporter, High-Affinity Potassium Transporters and Non-Selective Cation Channel (Kronzucker and Britto, 2011). High-Affinity Potassium transporters are required for K⁺ uptake, root hair production and tolerance to abiotic stressors (Nieves-Cordones et al., 2014). They may, nevertheless, play a crucial function in facilitating Na⁺ absorption. Indeed, several members of this family have been demonstrated to mediate high-affinity Na+ uptake.

As a result of salt stress, some species have developed mechanisms to maintain a high K⁺/Na⁺ and Ca²⁺/Na⁺ ratios. These mechanisms include the selective uptake of K⁺ or Ca²⁺ over Na⁺, the exclusion of Na⁺ from uptake, the compartmentalization of Na⁺ in vacuoles in the root cells, and the transport of Na⁺ back to the soil through the salt glands or leaf excretion (Parihar et al., 2015; Isayenkov and Maathuis, 2019; Acosta-Motos et al., 2020). Maintaining a high K⁺/Na⁺ and Ca²⁺/Na⁺ ratios in plant tissues can be critical for plant survival under salinity stress. Therefore, the K⁺/Na⁺ and Ca²⁺/Na⁺ ratios can be used as a diagnostic tool to assess plant tolerance to salinity stress. By measuring the K⁺/Na⁺ and Ca²⁺/Na⁺ ratios in plant tissues, growers and researchers can gain insights into the plant's response to salinity stress and develop strategies to enhance plant tolerance to salinity stress (Acosta-Motos et al., 2014; Liu et al., 2019; Bello et al., 2021). In our study, the saline treatment (S) shows the highest values in Na⁺ and Cl^- ions and the lowest values for both ratios in leaves and stems. On the contrary, the severe deficit treatment (SW) showed the highest values in K⁺ and Ca²⁺ ions and both ratios also in the same organs. Also, this nutritional behaviour associated with the saline treatment (S) and severe water deficit treatment (SW) made it possible to separate them very well, especially because of the importance of K⁺ and Na⁺ and other nutrients as Mg²⁺ and Ca²⁺ in PC1 and due to the Na⁺ and Cl^- ions in PC2. Therefore, other nutrients in leaves, as Mg²⁺ or Ca²⁺, also are important. Mg ²⁺ can have a higher demand as a nutrient for chlorophyll synthesis (as it is part of its chemical structure), which is essential for carrying out a more efficient process of photosynthesis and increasing the water use efficiency (WUE) under stress situations (Dias et al., 2017; Tränkner et al., 2018; Ouled Youssef and Krouma, 2021). In our study, a higher concentration of Mg²⁺ in leaves could optimise the photosynthetic process despite increased stomata closure in the SW and MW treatments (especially in SW) contributing to an increase in WUE. Ca²⁺ is crucial to ensure the maintenance of cellular rigidity, as it plays a vital role in the stiffness and stability of cell walls (as it is part of their chemical composition). Ca²⁺ helps maintain the structural integrity of cells and prevents them from collapsing or being damaged under water stress conditions. Additionally, Ca²⁺can improve cellular turgor or maintain proper cellular turgor even under severe deficit irrigation conditions contributing to cell survival and normal functioning (Ahanger et al., 2013; Kour et al., 2023). In our study, a higher concentration of Ca²⁺ in leaves could assume the same roles as indicated above in the SW and MW treatments (especially in SW).

The relative water content (RWC) at predawn and midday are commonly used time points to assess changes in plant water status. RWC at predawn reflects plant water potential and indicates the level of water stress. Since photosynthesis and transpiration haven't started yet, there is no additional water loss during this time. On the other hand, RWC at midday can indicate plant water use efficiency. A higher RWC at midday suggests the plant maintains good hydration despite transpiration, while a lower RWC indicates water stress (Gindaba et al., 2005). In our study, moderate water deficit led to higher RWC values at predawn during summer months compared to the control. RWC values at midday were more affected by irrigation restriction, with lower values in severe treatments. Saline treatment showed little difference from the control. RWC is more sensitive to water stress than salt stress due to its definition as a measure of plant hydration. Water stress reduces RWC, while salinity stress hampers water absorption. RWC is a more rapid and sensitive indicator of water stress compared to plant growth and yield affected by salinity stress. RWC values in drought treatments recover after the hottest months, as cooler temperatures reduce water stress and enhance water uptake. Recovery depends on factors like severity and duration of stress, plant species, tolerance, and soil water availability (Toscano et al., 2019). During hot and dry months, water stress can cause a decline in RWC, potentially leading to plant damage or death (Alhaithloul, 2019). However, if the stress is not severe, the plant can recover RWC during cooler and wetter months (Galmés et al., 2007). Cooler temperatures reduce transpiration and slow water loss, maintaining or increasing RWC. They also increase soil water-holding capacity, supplying more water for plant uptake and aiding RWC recovery (Juenger and Verslues, 2023).

In a similar way to RWC, leaf water potential can vary throughout the day due to changes in plant water status, with different values typically observed at predawn and midday and it has also demonstrated usefulness as a stress index in a large number of species (Álvarez et al., 2019; Sánchez-Blanco et al., 2019; Álvarez et al., 2020). The difference between the leaf water potential at predawn and midday can be used to evaluate the plant's ability to maintain its water status throughout the day. A smaller difference between the two values indicates that the plant is able to maintain its water status during the day and that it has good water use efficiency, while a larger difference indicates that the plant is experiencing water stress during the day and that it may not be using water efficiently. In our study, as one would expect the changes in leaf water potential were more evident in predawn that in midday due to the influence of environmental factors as mentioned above and more pronounced in drought treatments during the summer months.

During drought and saline conditions, the availability of water in the soil decreases, and plants often experience water stress and as a result, the stem water potential of the plant also decreases (Pérez-Pérez et al., 2009; Yang et al., 2020). When water is readily available in the soil, the plant takes up water through its roots and this water is transported through the plant's vascular system to the leaves. This movement of water is driven by differences in water potential between the soil, the plant, and the atmosphere (Berry et al., 2019; Scharwies and Dinneny, 2019). When soil water availability decreases due to drought or salinity, the plant's ability to take up water is reduced, and water transport through the plant is also affected. As the plant attempts to cope with water or salt stress, it may reduce its transpiration rate and water use to conserve water (Bertolino et al., 2019). This could result in a decline in stem water potential as the plant attempts to maintain water balance and avoid tissue damage (Levy et al., 2013; Lugassi et al., 2019). In some cases, the stem water potential may decrease to a level that is so low that the plant wilts or even dies (Abideen et al., 2021). In our study, depending on the month analysed and especially in the summer months, sometimes it is the saline treatment or the severe deficit irrigation, the treatments that show the lowest values in stem water potential. To cope with low stem water potential, plants can develop various mechanisms to optimize water use and minimize water loss. Some of these mechanisms include stomatal regulation, root and leaf adaptations, dormancy and shedding, or cellular protection. In our study, Pistacia lentiscus plants regulated the opening and closing of stomata to control water loss through transpiration and plants subjected to saline and water deficit produced osmoprotectants and antioxidants in order to help protect cells from damage caused by dehydration and oxidative stress. These mechanisms collectively help plants survive and adapt to low stem water potential by reducing water loss, optimizing water uptake, and maintaining essential physiological processes as much as possible during challenging conditions.

Plants increase their osmotic adjustment in response to salt or drought stress, which results in the accumulation of osmolytes like soluble sugars, amino acids, and organic acids, in plant cells in response to a depletion of the available soil moisture (Callister et al., 2006; Singh et al., 2015; Khan et al., 2020). This allows the plant to maintain its turgor pressure and prevent wilting. Osmotic adjustment is closely related to the leaf water potential and relative water content of the plant. Maintaining high RWC at low leaf water potentials is primarily related to osmotic adjustment, which could be considered as a strategy to tolerate water stress (Pérez-Pérez et al., 2009; Banks and Hirons, 2019). In our study, P. lentiscus plants submitted to water stress and salinity showed osmotic adjustment, which was more pronounced under salinity than under both levels of water deficit. NaCl-induced osmotic adjustment is also a common response to salinity stress caused by high concentrations of salt in the soil or irrigation water (Zhang et al., 2022). To counteract the decrease in water availability due to high salt concentration, plants can adjust their osmotic potential by accumulating solutes, sugars, and amino acids, in their cells. However, the effectiveness of osmotic adjustment in alleviating the effects of salinity stress depends on the plant species and cultivars, as well as the concentration and duration of the salt stress (Liao et al., 2022; Egea et al., 2023). In our study, Pistacia lentiscus might exhibit some tolerance to a salinity level of 4 dS m^-1, but it's essential to remember that "tolerance" doesn't mean thriving. Even tolerant plants can show signs of stress and reduced growth under elevated salt conditions. Pistacia lentiscus is known to have some degree of salt tolerance, but its exact response to different salinity levels can vary. In our study, P lentiscus plants irrigated with salinity level of 4 dS m^-1 during 11 months reduced growth, altered nutrient uptake, increased the osmotic adjustment and reduced gas exchange parameters.

The findings from our study indicate that the observed reduction in g_s is an adaptive and efficient mechanism used by the species to control transpiration (Hatfield and Dold, 2019). This mechanism helps the plant can withstand salinity and water stress, particularly during periods of high transpiration. In the case of plants under deficit irrigation conditions, this mechanism limits water loss (Lefi et al., 2023). For saline plants, the reduction in g_s helps to decrease the salt load on leaves, thus increasing longevity by keeping salts at subtoxic levels for a longer time (Izadi et al., 2022). The delay in the reduction of g_s in saline plants as compared to deficit irrigation plants is due to the time it takes for salts to accumulate inside the plant before reaching toxic levels that could affect plant functioning (Munns, 2011; Pirasteh-Anosheh et al., 2016). Similar changes in P_n were observed also in g_s between the treatments studied. The P. lentiscus plants that were subjected to both deficit irrigation treatments exhibited an increase in their intrinsic water use efficiency (P_n/g_s), particularly during periods of high-water demand. An increase in intrinsic water use efficiency (P_n/g_s) in plants indicates that they are able to photosynthesize and produce the same amount of biomass while using less water, which is an important adaptation for plants growing in environments with water scarcity and salt stress (Fernández-García et al., 2014; Liao et al., 2022). Plants face a constant dilemma: to die of thirst or to die of hunger. This is because plants need water to carry out photosynthesis and produce energy, but they also need nutrients such as nitrogen, phosphorus, and potassium to grow and develop. If plants do not receive enough water, their ability to photosynthesize is compromised, reducing their energy production capacity and ultimately leading to plant death by dehydration (Chaves et al., 2016). On the other hand, if plants do not receive enough nutrients, their growth is affected, and their energy production capacity is also reduced, leading to death by starvation. To survive, plants must find a balance between water and nutrient uptake and water loss through transpiration. This is achieved by regulating stomatal aperture, which controls the entry and exit of water and gases in the plant (Bhattacharya, 2021). While this balance may vary depending on environmental conditions and plant species, most plants have evolved to optimize their efficiency in using water and nutrients and to adapt to variable conditions in their environment.

It can be inferred that the application of moderate and severe deficit irrigation (60 and 40 % reductions with respect to the control) and the use of saline water with a determined level of salinity (around 4 dS m^-1) is feasible for growing this species. Based on its observed behaviour when applying deficit irrigation strategies and irrigation with low quality water, Pistacia lentiscus is proposed as a suitable species for gardening projects and landscaping in arid and saline areas

The original contributions presented in the study are included in the article/ Supplementary Material , further inquiries can be directed to the corresponding author.

SA performed the experiment and drafted the manuscript. MS-B and SA designed and instructed the research work. SA and JA-M carried out statistical analysis. MS-B also coordinated the study and provided study material and facilities for the experiments. The three authors were involved in data interpretation, paper preparing and article writing. All authors have read and approved the final manuscript.